Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$65.61	10.578%	$72.5502	$72.55	$72.55	$72.60
Purchase #2	$139.85	9.149%	$152.6449	$152.64	$152.65	$152.60
Purchase #3	$39.98	11.638%	$44.6329	$44.63	$44.65	$44.60
Purchase #4	$219.49	4.646%	$229.6875	$229.69	$229.70	$229.70
Purchase #5	$185.37	13.175%	$209.7925	$209.79	$209.80	$209.80
Purchase #6	$59.83	11.197%	$66.5292	$66.53	$66.55	$66.50
Purchase #7	$76.40	7.447%	$82.0895	$82.09	$82.10	$82.10
7 purchase totals =	$786.53		$857.9267	$857.92	$858.00	$857.90